As is known, solar trackers are used to improve photovoltaic panel production by capturing maximum solar energy radiation during the longest possible time through systems following the path of the sun.
Many companies market solar trackers and there are many models with both single and dual-axis tracking, all of them having a series of common features discussed below:
Panel clustering in the smallest possible space by means of forming large surfaces at a single level.
This solution hinders panel cooling, reducing their yield due to the temperature increase at a ratio of 0.5% per ° C. This clustering is further limited due to panel expansion since the support structures are rigid and occasionally surrounded by a frame enclosing them, generating stresses between panels due to nighttime and daytime temperature differences. In most cases, the panels are fixed with anchors on the two shafts, preventing their expansion.
Another significant drawback is that resulting from their stability given that since they are planar surfaces, the anchor and rotation points are located outside the plane passing through their center of gravity, causing asymmetrical static loads limiting their weight and dimensions so as to not overload the rotation points.
This situation is worsened by the stresses resulting from the wind which generate thrusts and overturning moments making them rather unstable.
On the other hand, when carrying out what is known as “solar farms” by means of tracker clustering, it is necessary to use a large number of trackers, which requires occupying more terrain due to shadows, among other factors, which increases final costs in bases, trenches and electrical infrastructures.
Of the two solar tracker axes, azimuthal orientation and tilt, the first one is important since it provides a production gain in the order of 30%, while the second axis controlling tilt provides a gain in the order of 8%, being less significant.
The azimuth tracking axis can furthermore be easily carried out since it is exclusively a time function and therefore uniform throughout the year; the second axis, the tilt axis, varies according to the ellipse of the sun, and its tracking is more complex and occasionally, due to its little gain, it is not worth carrying it out since it complicates the tracker mechanism and reduces its strength.
In fact most large trackers installed until now have only single-axis tracking.
Another aspect to be taken into account is the lack of foresight with respect to future expansions since most investors in this field at first have doubts or limited resources and begin with smaller installations which in a short time are to be expanded. This expansion is complicated and expensive if it has not been foreseen from the beginning.
The advances in this field involve the design of larger, stronger and more reliable trackers designed for a useful life of up to 25 years, which are less sensitive to the wind and provide the panels, and therefore inverters, with better conditions of durability and performance, in turn reducing the specific costs.
The new Royal Decree 436/2004, dated March 12, increases the premium price for photovoltaic electrical generation up to 100 kW, therefore the manufacture of large trackers is currently required to move forward in this matter.